Department of
Materials Science and Engineering
2005 Spring Seminar Series
April 15
3:30 - 4:30, 331 Randolph
Polymagnets
Dr. Harsh
D. Chopra
Thin Films and Nanosynthesis Laboratory
Materials Program
Mechanical and Aerospace Engineering Department
SUNY-Buffalo
Buffalo, NY
Abstract
This work will discuss the temperature
and field-dependent evolution of the micromagnetic structure
in ferromagnetic shape memory alloys (Ni-Mn-Ga, Fe-Pd,
and Co-Ni-Ga). These results answer a fundamental question,
viz., what is the nature of the magneto-elastic coupling
in these alloys and to what extent does it drives the
structural transformation? It is shown that the temperature
dependent reconfiguration of the micromagnetic structure
is completely enslaved to and follows the martensitic
transformation in these alloys. In analogy with ferro-elastic
polydomains, results provide a new and simple perspective
on these actuator materials – the micromagnetic structure
of these alloys resembles a magnetic ‘mosaic’
contained within ‘tiles’ of the transformed
martensite phase (twins), i.e., a ‘polymagnet’.
Polymagnets have a hierarchical complexity that mirrors
the underlying polydomain structure.
Biographical
Information
Harsh Deep Chopra (pronounced as ‘Hersh’) is Associate
Professor in Mechanical & Aerospace Engineering Department
at SUNY-Buffalo, which hosts the Materials Program at Buffalo.
Chopra graduated from the University of Maryland’ Materials
Department in December 1993. After his postdoctoral experience,
he joined SUNY-Buffalo in January 1998. Chopra’s primary
research interests are focused on magnetic functional material
(magnetic shape memory alloys, magnetostrictive materials)
in thin films, multilayers, and bulk form; and spintronics:
single-atom spintronics, GMR, and various forms of exchange
couplings.
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